Baroness Orczy wrote the novel The Scarlet Pimpernel in 1905, and went on to write several other novels about Percy and his activities. (The following list is in the order they were written, *not* in order of how events appear in the books).
I Will Repay - 1906
The Elusive Pimpernel - 1908
Eldorado - 1913
The Laughing Cavalier - 1914
Lord Tony's Wife - 1917
The League of the Scarlet Pimpernel - 1919
The First Sir Percy - 1920
The Triumph of the Scarlet Pimpernel - 1922
Pimpernel and Rosemary - 1924
Sir Percy Hits Back - 1927
Adventures of the Scarlet Pimpernel - 1929
The Way of the Scarlet Pimpernel - 1933
Sir Percy Leads the Band - 1936
Mam'zelle Guillotine - 1940
You can view the complete e-texts of the novels online at Blakeney Manor.